Clutch and work machine having same

ABSTRACT

The present invention provides a clutch and a work machine having same. The clutch comprises an input member for receiving a driving force and rotating, an output member for outputting rotational motion, and at least one transmission member. The input member has at least one radially extending protrusion. The output member has at least one transmission engagement part. The transmission member is movable between a first position of engagement with the transmission engagement part and a second position of disengagement, being located in a path of rotation of the protrusion, and able to abut the protrusion and be driven to move to the first position. Displacement of the transmission member between the first position and second position has a radial component. According to the technical solution of the present invention, the function of automatically switching between transmission states according to the operating state of a prime mover can be achieved. The fact that displacement of the transmission member comprises a radial component helps to reduce the axial thickness of the clutch, so that the structure thereof is more compact.

TECHNICAL FIELD

The present invention relates to a clutch and a work machine havingsame.

BACKGROUND ART

Walk-behind work machines such as lawnmowers are generally provided withwheels for movement. The wheels enable the operator to move thewalk-behind work machine to different work sites to performcorresponding work tasks. In some application scenarios, the operatormay provide the driving force needed to move the work machine. In otherapplication scenarios, the driving force may also be provided by aprimer mover (such as a motor or internal combustion engine) provided onthe work machine, the prime mover being coupled to the wheels by meansof a transmission apparatus (such as a gearbox comprising a clutch), torealize transmission of the driving force, in which case the workmachine may have a self-propulsion function.

When the driving force is provided by a prime mover, it is desirablethat the transmission apparatus be able to provide a stable andefficient transmission coupling. When an external traction forceprovided by the operator or another external apparatus serves as thedriving force (in particular in a state in which the prime mover hasstopped operating), it is desirable that the transmission apparatus beable to break the transmission coupling between the prime mover and thewheels, to prevent the prime mover from rotating with the wheels andcausing a large amount of resistance. At present, walk-behind workmachines are generally provided with a control apparatus such as acontrol rod and pull wire; the operator can switch manually betweenstates of the transmission apparatus by means of the control apparatus,to establish or break the transmission coupling according to differentoperating modes. Such a manner of operation requires manual interventionand is quite complex, and is unable to achieve automatic switchingbetween states of the transmission apparatus according to the operatingstate of the prime mover.

Thus, there is a need to provide an alternative solution to at leastpartially alleviate or mitigate the abovementioned shortcomings.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a clutch and a workmachine having same, to achieve automatic switching between transmissionstates of a transmission apparatus according to the operating state of aprime mover while providing other additional advantages, such as thestructure of the transmission apparatus being smaller and more compact,realizing a differential function, etc.

A clutch according to one aspect of the present invention comprises:

an input member, the input member being configured to receive a drivingforce and rotatable about a rotation axis under the action of thedriving force, the input member having at least one protrusion extendingin a radial direction relative to the rotation axis;

an output member, the output member being configured to outputrotational motion and having at least one transmission engagement part;

at least one transmission member, the at least one transmission memberbeing configured to be movable between a first position in which it isengageable with the transmission engagement part and a second positionof disengagement, the at least one transmission member being located ina path of rotational motion of the protrusion, and able to abut theprotrusion and be driven to move to the first position, whereindisplacement of the at least one transmission member between the firstposition and the second position has a component in the radialdirection.

In some embodiments, the clutch further comprises a biasing member,which biases the at least one transmission member towards the secondposition.

In some embodiments, the biasing member is a spring, the spring havingone end coupled to the at least one transmission member, and another endcoupled to the input member or a mounting member for mounting the atleast one transmission member.

In some embodiments, the at least one transmission member is able toabut the protrusion and be driven to move to the second position.

In some embodiments, a sharp bump is provided at an inner side of the atleast one transmission member, the sharp bump being able to abut theprotrusion when the input member rotates in a direction opposite to adrive direction.

In some embodiments, the clutch is configured such that the input memberrotates through a predetermined angle in a direction opposite to a drivedirection when the outputting of rotational motion is stopped.

In some embodiments, the at least one transmission member moves in aplane perpendicular to the rotation axis.

In some embodiments, the at least one transmission member moves in theplane between the first position and the second position along astraight line inclined relative to the radial direction.

In some embodiments, the protrusion comprises three protrusions arrangedat uniform intervals in the circumferential direction about the rotationaxis, and the at least one transmission member comprises threetransmission members arranged in one-to-one correspondence with theprotrusions.

In some embodiments, the transmission engagement part of the outputmember comprises a stop wall extending parallel to the rotation axis,the at least one transmission member abutting the stop wall to achieveengagement with the transmission engagement part.

In some embodiments, the stop wall extends substantially in the radialdirection.

In some embodiments, when the at least one transmission member islocated at the second position, the at least one transmission member islocated outside a path of rotational motion of the stop wall.

In some embodiments, the output member is provided with a cam surfaceextending parallel to the rotation axis; the cam surface is locatedbetween two adjacent stop walls, and connects a radially outside end ofone of the stop walls to a radially inside end of the other adjacentstop wall, at least part of the cam surface being a curved surface.

In some embodiments, in the direction of the driving force, the angularvelocity of rotation of the output member is greater than or equal tothe angular velocity of rotation of the input member.

In some embodiments, the clutch further comprises a mounting member formounting the at least one transmission member, the mounting member beingprovided with an elongated slot defining a movement path of the at leastone transmission member between the first position and the secondposition.

In some embodiments, the elongated slot comprises a curved surface, toallow the at least one transmission member to pivot in the elongatedslot.

In some embodiments,

the output member is provided with a recess, and at least one of the atleast one transmission member, the mounting member and the input memberis at least partially disposed in the recess; or

the input member is provided with a recess, and at least one of the atleast one transmission member, the mounting member and the output memberis at least partially disposed in the recess.

In some embodiments, the mounting member is provided with a mountingslot formed as a sunken cavity, the input member being accommodated inthe sunken cavity.

In some embodiments, the mounting member is provided with a dampingelement, the damping element being configured to be able to providedamping so that the mounting member tends to remain stationary.

In some embodiments, the damping element provides damping by rubbingagainst a member other than the input member and the transmissionmember, in particular by rubbing against a transmission caseaccommodating the clutch.

In some embodiments, the damping element is made of a rubber or siliconerubber material, and extends radially outwards relative to the mountingmember.

A work machine according to another aspect of the present inventioncomprises a prime mover, at least one wheel and the clutch as describedabove, the prime mover driving the input member of the clutch, and theoutput member of the clutch driving at least one of the at least onewheel to rotate.

In some embodiments, the work machine comprises two clutches arranged ina mirror-image fashion, each clutch being coupled to at least onecorresponding wheel.

In some embodiments, the work machine is a gardening tool, in particulara lawnmower or a snow blower.

The clutch and work machine according to the present invention are ableto achieve the following beneficial effects:

1) The transmission member can move automatically to the first positionof engagement with the output member under the action of the radiallyextending protrusion of the input member, and can move automatically tothe second position of disengagement from the output member under theaction of the biasing member when the input member stops moving. Thefunction of automatically switching between transmission statesaccording to the operating state of the prime mover is thereby achieved.

2) Displacement of the transmission member between the first positionand second position comprises a radial component, helping to reduce theaxial thickness of the clutch along the rotation axis, so that thestructure of the clutch is more compact.

3) In some preferred embodiments, a speed differential function can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

To better understand the above and other objectives, features,advantages and functions of the present invention, the preferredembodiments shown in the drawings may be referred to. In the drawings,identical reference labels denote identical components. Those skilled inthe art should understand that the drawings are intended to illustratepreferred embodiments of the present invention schematically, and haveno limiting effect on the scope of the present invention, and thevarious components in the drawings are not drawn to scale.

FIG. 1 is a 3D drawing of a work machine according to a preferredembodiment of the present invention.

FIG. 2 is a 3D drawing of the work machine shown in FIG. 1 , viewed fromanother angle.

FIG. 3 is a 3D drawing of a clutch according to a preferred embodimentof the present invention.

FIG. 4 is a 3D drawing of the clutch shown in FIG. 3 , viewed fromanother angle.

FIG. 5 is a schematic drawing of the clutch shown in FIG. 3 in adisengaged state, with the mounting member omitted.

FIG. 6 is a schematic drawing of the clutch shown in FIG. 3 in anengaged state, with the mounting member omitted.

FIG. 7 is a rear view of the clutch shown in FIG. 3 , with the outputmember omitted, showing a biasing member configured as a spring.

FIG. 8 is a front view of a clutch according to another preferredembodiment of the present invention.

FIG. 9 is a 3D view of a clutch according to another preferredembodiment of the present invention.

FIG. 10 shows a transmission path of a work machine according to thepresent invention, from the prime mover to the clutch; and

FIG. 11 is part of a sectional view taken along line A-A in FIG. 10 .

KEY TO THE DRAWINGS

1 lawnmower

10 base

11 cutting tool

12 wheel

13 hand support frame

20 prime mover

201 output shaft

21 transmission apparatus

211 first gear

212 second gear

213 third gear

214 fourth gear

215 fifth gear

216 coupling shaft

22 transmission case

30/30′/30″ clutch

31/31′ input member

311 input engagement part

312 protrusion

32/32′ output member

321 output engagement part

322 transmission engagement part

323 cam surface

323 a downstream end

323 b upstream end

324 recess

33/33′ transmission member

331 pin structure

332 sharp bump

34/34″ mounting member

341 elongated slot

342 fastener

343 first mounting slot

344 second mounting slot

345 damping element

346 holding part

35 spring

40 drive shaft

AX rotation axis

F drive direction

F1 direction opposite to drive direction

DETAILED DESCRIPTION OF EMBODIMENTS

Particular embodiments of the present invention are now described indetail with reference to the drawings. The embodiments described hereare merely preferred embodiments of the present invention. Based onthese preferred embodiments, those skilled in the art will be able tothink of other ways in which the present invention could be implemented,all of which likewise fall within the scope of the present invention.

The present invention provides a work machine, in particular a gardeningtool, which is able to move between different positions by means ofwheels under the action of an external traction force and/or a drivingforce provided by its own prime mover. In addition, the presentinvention further provides a clutch for the work machine. The clutch isdisposed between the prime mover and the wheels, and used to transmitthe driving force of the prime mover to the wheels.

The work machine is preferably provided with a hand support frame, tofacilitate gripping and application of force by the operator. Such awork machine may also be called a walk-behind work machine. One exampleof a walk-behind work machine is a lawnmower, which is configured to beable to move over the growth surface of grass or a lawn and be operatedto perform a grass-cutting function. Such an action is usually referredto as “trimming a lawn”, and is generally performed by a gardener orlandscape worker to maintain the surface of the lawn. In addition, otherexamples of walk-behind work machines may be snow blowers, plowingmachines, micro tillers and wheeled vacuum cleaners. Preferredembodiments according to the present invention are presented in detailbelow with reference to the drawings.

FIGS. 1 and 2 show a lawnmower 1 as an example of the work machineaccording to the present invention, at least comprising a base 10, acutting tool 11, wheels 12, a hand support frame 13, a prime mover 20and a transmission apparatus 21. The cutting tool 11 is disposed at thebottom of the base 10, and can perform a job under the action of adriving force provided by the prime mover 20, to cut and clear weeds ona lawn. The wheels 12 are used to support the lawnmower 1 on a workingsurface (such as a lawn), and can rotate under the action of a drivingforce provided by the prime mover 20, to move the lawnmower 1 betweendifferent positions. The same prime mover 20 may be used to provide thedriving forces to the wheels 12 and the cutting apparatus 11respectively, or different prime movers 20 may be provided to providethe driving forces separately. In the embodiment shown in the figures,the lawnmower 1 comprises four wheels 12, arranged opposite each otherat left and right sides of a front end and a rear end of the base 10respectively, to realize stable support. Of course, in otherembodiments, the number of wheels 12 may be set to one, two, three ormore as required. The hand support frame 13 is disposed at a rear partof the lawnmower 1 and is angled upwards obliquely towards the rear, sothat it can be conveniently gripped by the operator in the course ofworking to push the lawnmower 1 forwards and backwards.

Referring to FIG. 2 , the prime mover 20 is disposed at the rear end ofthe base 10, close to the wheels 12 located at the rear end. Thetransmission apparatus 21 is located between the prime mover 20 and thewheels 12, and used to transmit a driving force therebetween. An exampleof the prime mover 20 could be an electric motor or internal combustionengine, etc., which may be configured to provide a driving force to onlyone wheel 12, or may provide a driving force simultaneously to two ormore wheels 12. It is also possible to provide more than one primermover 20 and transmission apparatus 21, to drive multiple wheels 12separately. In the case where the prime mover 20 provides a drivingforce, a driven wheel 12 may be called a driving wheel, and a wheel 12which rotates passively as the lawnmower 1 moves may be called a drivenwheel. In the embodiment shown, the two wheels 12 close to the rear endof the base 10 are driven by the prime mover 20, so are driving wheels.The two wheels close to the front end of the base 10 are driven wheels.

FIG. 10 shows the transmission path from the prime mover 20 to thedriving wheels via the transmission apparatus 21. In some embodiments,the transmission apparatus 21 comprises a transmission gear train and aclutch. An output shaft of the prime mover 20 is transmission-coupled tothe clutch 30 via the transmission gear train, and furthertransmission-coupled to the driving wheels via the clutch 30. In theembodiment shown, an extremity of the output shaft 201 of the primemover 20 is configured in the form of a gear, and meshed with a firstgear 211 of the transmission gear train. The output shaft 201 and thefirst gear 211 have substantially the same linear velocity. However, thediameter of the first gear 211 is greater than the diameter of theoutput shaft 201, so the speed outputted by the prime mover 20 isreduced a first time at the first gear 211. The first gear 211 and asecond gear 212 are arranged coaxially, and have substantially the sameangular velocity. The second gear 212 and a third gear 213 are meshed,and have substantially the same linear velocity, but the diameter of thethird gear 213 is greater than the diameter of the second gear 212.Thus, the speed outputted by the prime mover 20 is reduced a second timeat the third gear 213. The third gear 213 is further arranged coaxiallywith a fourth gear 214. The fourth gear 214 and a fifth gear 215 aremeshed, and have substantially the same linear velocity, but thediameter of the fifth gear 215 is greater than the diameter of thefourth gear 214. Thus, the speed outputted by the prime mover 20 isreduced a third time at the fifth gear 215. It will be understood thatin different embodiments, it is possible to flexibly choose the numberof stages in the transmission gear train and whether the transmissionresult is a reduction in speed or an increase in speed, according toactual needs.

As shown in FIG. 11 , the fifth gear 215 forms a final-stage gear of thetransmission gear train. Furthermore, the transmission gear trainfurther comprises a coupling shaft 216 arranged coaxially with the fifthgear 215. Optionally, the final-stage gear of the transmission geartrain is transmission-coupled to two clutches 30 simultaneously. Thesetwo clutches 30 are arranged substantially in a mirror-image fashionrelative to the final-stage gear. Output ends of the two clutches 30 arecoupled to respectively corresponding drive shafts 40. An extremity ofeach drive shaft 40 is further coupled to one driving wheel (not shown)respectively. For example, the extremity of the drive shaft 40 may becoupled to the driving wheel directly via a pin or splines, etc.Alternatively, a gear structure may be provided at the extremity of thedrive shaft 40, and a ring gear may be provided on the driving wheel,with the transmission coupling being accomplished by meshing of the gearstructure with the ring gear. In this way, the lawnmower 1 is able todrive the two driving wheels at the left and right sides simultaneouslyby means of a single prime mover 20 cooperating with a singletransmission apparatus 21. The transmission gear train and the clutches30 form the main part of the transmission apparatus 21. Furthermore, atransmission case 22 is also provided, in which the transmission geartrain and the clutches 30 are accommodated, and which serves aprotecting function, preventing the ingress of debris while alsoproviding lubrication for the transmission gear train and otherstructures. Furthermore, having the clutches arranged in a mirror-imagefashion can allow a speed differential (described in detail below) toarise between the driving wheels respectively corresponding to the twoclutches, thereby allowing the work machine to accomplish a turningaction without the prime mover 20 stopping operation, thus making iteasier to operate the work machine.

FIGS. 3-6 show the clutch 30 according to some embodiments of thepresent invention, mainly comprising an input member 31, an outputmember 32 and transmission members 33.

The input member 31 for example has an input engagement part 311configured as an internal spline structure, and may be coupled to theprime mover 20 directly (not via a drive train) or indirectly (via adrive train) by means of the input engagement part 311, thereby beingable to receive a driving force from the prime mover 20, and rotatearound a rotation axis AX in a drive direction F under the action of thedriving force. The output member 32 is used to output rotational motionto the outside, and for example has an output engagement part 321configured as an internal spline structure, and may be coupled to atleast one wheel 12 directly or indirectly by means of the outputengagement part 321, thereby being able to drive at least one wheel 12to rotate. As shown in FIG. 10 , in some embodiments, the inputengagement part 311 is coupled to the prime mover 20 via thetransmission gear train, while the output engagement part 321 is coupledto the wheel 12 (driving wheel) via the drive shaft 40.

The transmission members 33 are movably arranged between the inputmember 31 and the output member 32. When the transmission members 33 arelocated at a first position as shown in FIG. 6 , they can engage withthe output member 32, transmitting the rotational motion of the inputmember 31 to the output member 32, such that the output member 32rotates together with the input member 31. At this time, the clutch 30is in an engaged state. When the transmission members 33 move to asecond position as shown in FIG. 5 , they disengage from the outputmember 32, at which time there is no driving force acting on the outputmember 32 via the input member 31, so the output member 32 remainsstationary. The clutch 30 is in a disengaged state. The transmissionmembers 33 may also be called movable pawls.

It will be understood that during normal driving, the input member 31drives the output member 32 to rotate by means of the transmissionmembers 33, in turn driving the wheel 12 to rotate by means of the driveshaft 40. At this time, the input member 31 and the output member 32have substantially the same angular velocity of rotation. As statedabove, in some embodiments, two clutches 30 are transmission-coupled tothe same final-stage gear, and arranged in a mirror-image fashionrelative to the final-stage gear. Furthermore, the clutch 30 isconfigured to allow the angular velocity of rotation of the outputmember 32 to be greater than the angular velocity of rotation of theinput member 31. In this way, when the operator applies an externaltraction force to the wheel 12 at one side or applies unbalancedexternal traction forces to the wheels 12 at both sides, the wheel 12 atone side acted on by the larger force has a greater rotation speed thanthe wheel 12 at the other side acted on by the smaller force, i.e. aspeed differential forms, at which time the work machine is able toaccomplish a turning action. Since the angular velocity of rotation ofthe output member 32 of the clutch can be greater than the angularvelocity of rotation of the input member 31, such an operation canautomatically achieve a speed differential effect, without the need tomanually switch the clutch 30 to the disengaged state. When the externaltraction force disappears, the clutch 30 will automatically re-enter theengaged state under the action of the driving force of the prime mover20.

According to the present invention, when the driving force acts on theinput member 31, the clutch 30 can automatically switch to the engagedstate without the need for active operation by the operator, to outputrotational motion to the outside. Specifically, referring to FIGS. 5 and6 , the input member 31 has protrusions 312 extending outwards in radialdirections relative to the rotation axis AX. The transmission members 33are disposed in the path of rotational motion of the protrusions 312.When the driving force acts on the input member 31, the protrusions 312rotate around the rotation axis AX, and thereby contact the transmissionmembers 33. As the rotational motion continues, the transmission members33 are driven to move to the first position shown in FIG. 6 under theaction of the protrusions 312.

The output member 32 is provided with transmission engagement parts 322.In the embodiment shown, the transmission engagement parts 322 areconfigured in the form of stop walls extending substantially parallel tothe rotation axis AX. When the transmission members 33 move to the firstposition, they abut the stop walls, thereby engaging with thetransmission engagement parts 322. Thus, the transmission members 33transmit the action force of the protrusions 312 to the transmissionengagement parts 322, so that the output member 32 rotates together withthe input member 31. The clutch 30 automatically switches to the engagedstate. Preferably, the stop walls extend substantially in said radialdirections.

In some embodiments, the clutch 30 is further provided with biasingmembers, which apply a biasing force to the transmission members 33 tobias them towards the second position. As shown in FIG. 7 , the biasingmember may for example a spring 35, having one end coupled to thetransmission member 33, and another end coupled to the protrusion 312which drives the transmission member 33 to move towards the firstposition. Preferably, the clutch 30 is further configured such that whenthe outputting of rotational motion is stopped, the input member 31rotates through a predetermined angle in a direction F1 (see FIG. 8 )opposite to the drive direction. This configuration may be accomplishedby, for example, causing the prime mover to rotate in reverse for apredetermined time (e.g. 0.1 s) or through a predetermined angle afterceasing to operate. Thus, after the prime mover has ceased to operate,the input member 31 rotates in reverse through a predetermined angle, asufficient gap arises between the protrusion 312 and the transmissionmember 33, and the transmission member 33 can move from the firstposition to the second position shown in FIG. 5 under the action of thebiasing member, thereby causing the clutch 30 to automatically switch tothe disengaged state.

In some other embodiments, the biasing member may be omitted, and thetransmission member may be moved to the second position by theprotrusion of the input member abutting the transmission member.Referring to the clutch 30′ shown in FIG. 8 , a sharp bump 332 isprovided on an inner side of the transmission member 33′. When theoutputting of rotational motion is stopped, the input member 31′ rotatesthrough a predetermined angle in the direction F1 opposite to the drivedirection. In the course of rotating in reverse, the protrusion 312′abuts the sharp bump 332 of the adjacent transmission member 33′ locatedbehind (i.e. upstream of) the protrusion in the drive direction F. Asthe rotation in reverse continues, the protrusion 321′ drives thetransmission member 33′ to move to the second position. It will beunderstood that with such a configuration, the force applied to thesharp bump 332 by the protrusion 312′ is in a direction tangential tothe direction of rotation thereof, so might cause the transmissionmember 33′ to pivot in the process of moving towards the secondposition.

In the second position, the transmission members 33 are locatedcompletely outside the path of rotational motion of the transmissionengagement parts 322. At this time, the output member 32 can freelyrotate independently of the input member 31 and the transmission members33. In other words, if the operator wishes that the lawnmower 1 bedriven to move by an external traction force (such as a pushing orpulling force applied by the operator or another external driving means)when the prime mover 20 has stopped operating, the wheel 12 coupled tothe output member 32 of the clutch 30 need only drive the output member32 to rotate with it. No action force will arise between the outputmember 32 and the transmission members 33/input member 31 ortransmission gear train/prime mover 20. It is thus possible to reduceresistance when an external traction force drives the lawnmower 1.Moreover, at this time the wheel 12 can also drive the output member 32to rotate in reverse, without interfering with the transmission members33 or the input member 31. That is to say, the operator can pull thelawnmower 1 backwards.

As shown in FIG. 4 , preferably, the clutch 30 further comprises amounting member 34, configured as a disc-shaped structure and providedwith elongated slots 341. Correspondingly, the transmission members 33are provided with protruding pin structures 331. The transmissionmembers 33 may be mounted on the mounting member 34 by insertion of thepin structures 331 into the elongated slots 341. Preferably, theelongated slot 341 is a penetrating slot, and a fastener 342 comprisinga spacer and a screw is provided at an end of the pin structure 331. Thesize of at least the spacer is greater than the width of the elongatedslot 341, to prevent the pin structure 331 from coming out of theelongated slot 341. It will be understood that in another embodiment, itis also possible to have the elongated slot provided in the transmissionmember, and have the pin structure cooperating therewith provided on themounting member.

In addition, in an embodiment in which a biasing member is used to drivethe transmission member, the mounting member may also be used to providea force application point for the biasing member configured as a spring.One end of the spring is still coupled to the transmission member, whilethe other end is coupled to the mounting member, not to the protrusionof the input member as described above. The specific form of the springmay be chosen flexibly as required, e.g. a tension spring, a torsionspring, a coil spring, a specially-shaped spring, etc.

When the transmission member 33 moves between the first position and thesecond position, the pin structure 331 moves in the length direction ofthe elongated slot 341. Thus, the elongated slot 341 defines the path ofmovement of the transmission member 33 between the first position andthe second position. According to the present invention, the movementpath of the transmission member 33 has a component in a radial directionrelative to the rotation axis AX. That is to say, movement of thetransmission member 33 between the first position and the secondposition causes a change in the radial position thereof relative to therotation axis AX. Preferably, the movement path of the transmissionmember 33 lies completely within a plane perpendicular to the rotationaxis AX. That is to say, movement of the transmission member 33 betweenthe first position and the second position will not give rise to axialdisplacement along the rotation axis AX. Such a configuration helps toreduce the axial thickness of the clutch 30 along the rotation axis AX,and will not give rise to a change in the axial dimension duringoperation, so makes the structure thereof compact.

Further preferably, the path of movement of the transmission member 33between the first position and the second position is a straight linewhich is inclined relative to a radial direction. For example, themovement path may be substantially in a direction tangential to the pathof rotational motion of the protrusion 312, or may deviate from thistangential direction by a small angle; in this way, the action torqueapplied to the transmission member 33 by the protrusion 312 can bemaximized. Moreover, correspondingly, it is only necessary for theelongated slot 341 to be configured as a straight slot, so the structureis simple. However, it will be understood that the path of movement ofthe transmission member 33 between the first position and the secondposition may also be configured as a curve as required, i.e. theelongated slot 341 is a curved slot. In addition, the elongated slot maycomprise a curved surface, to allow pivoting of the transmission memberin the process of moving towards the second position, in an embodimentin which the protrusion is used to drive the transmission member towardsthe second position.

Referring to FIG. 7 , the mounting member 34 is provided with firstmounting slots 343. The first mounting slots 343 are substantiallyconfigured to be elongated in shape, and are open at a circumferentialside of the mounting member 34. The transmission members 33 areaccommodated in the first mounting slots 343, and are capable of movingalong the first mounting slots 343 to the first position in which theyproject through the openings thereof, and retreating to the secondposition. Thus, the first mounting slots 343 can also serve to definethe movement paths of the transmission members 33. In addition, asubstantially round second mounting slot 344 is further provided in amiddle region of the mounting member 34, the second mounting slotcommunicating with the first mounting slots 343. The input member 31 isaccommodated in the second mounting slot 344 and is freely rotatable inthe second mounting slot 344. Such a configuration can further reducethe axial thickness of the clutch 30.

It will be understood that if there is an action force between thetransmission member and the mounting member, for example a frictionalforce, then when the input member pushes the transmission member, thelatter might be unable to overcome the action force to move relative tothe mounting member to the first position, and will instead directlydrive the mounting member to rotate under the action of the actionforce. Since the transmission member has not moved to the firstposition, it will not engage with the output member, and the clutch willidle in the disengaged state.

To avoid this problem, referring to FIG. 9 , in the clutch 30″ accordingto some embodiments, the mounting member 34″ is provided with dampingelements 345, which can provide damping for the mounting member 34″, sothat it tends to remain stationary. The damping elements 345 may beentirely or partially made of a rubber or silicone rubber material witha large coefficient of friction, may extend radially outwards relativeto the mounting member 34″, and are in contact with an inner wall of thetransmission case mentioned above for example. In addition, the mountingmember 34″ is provided with holding parts 346 for mounting the dampingelements 345. When the input member rotates under the driving action ofthe prime mover, the protrusions of the input member abut thetransmission members and push them to move towards the first position.At this time, the damping elements 345 rub against the inner wall of thetransmission case, providing damping for the mounting member 34″, sothat it tends to remain stationary. In this way, the transmission memberis able to overcome the action force between the transmission member andthe mounting member 34″ under the pushing action of the input member,and move smoothly relative to the mounting member 34″ to the firstposition, so as to engage with the output member.

As shown in FIG. 5 , the output member 32 is provided with a recess 324sunk along the rotation axis AX; at least part of at least one of thetransmission members 33, the mounting member 34 and the input member 31is disposed in the recess 324. Such a configuration can likewise furtherreduce the axial thickness of the clutch 30 along the rotation axis AX.In another embodiment, when the input member has a larger radialdimension and the output member has a smaller radial dimension, it isalso possible to have the recess provided in the input member, and havethe transmission members, the mounting member and the output member atleast partially disposed in the recess.

It will be understood that at least one protrusion 312, at least onetransmission member 33 and at least one transmission engagement part 322may be provided, to enable transmission of the driving force. In theembodiment shown, the clutch 30 is provided with three sets ofprotrusions 312, transmission members 33 and transmission engagementparts 322 which are in one-to-one correspondence and cooperate with eachother; this three-set structure is distributed at uniform intervals inthe circumferential direction about the rotation axis AX. However, thenumbers of cooperating protrusions, transmission members andtransmission engagement parts may be chosen flexibly according tochanges in the dimensions and structure of the clutch; moreover, theprotrusions and transmission members are not necessarily in a one-to-onecorrespondence relationship with the transmission engagement parts, aslong as transmission of the driving force can be achieved. For example,in some embodiments, the number of transmission engagement parts may betwice that of the protrusions and transmission members, etc.

In some embodiments, the output member 32 is further provided with camsurfaces 323, configured as faces that face the transmission members 33and are substantially parallel to the rotation axis AX, and each havinga downstream end 323 a and an upstream end 323 b in the drive directionF, these two ends being respectively connected to two adjacenttransmission engagement parts 322. Specifically, in the embodiment shownin which the transmission members 33 are located at a radially innerside of the transmission engagement parts 322, the downstream end 323 aof the cam surface 323 is connected to a radially outside end of thecorresponding stop wall, while the upstream end 323 b of the cam surface323 is connected to a radially inside end of the corresponding stop wall(i.e. the adjacent stop wall located behind the stop wall connected tothe downstream end 323 a in the drive direction F). Preferably, at leastpart of the cam surface 323 is a smooth curved surface.

As an alternative embodiment, when the transmission members are locatedat a radially outer side of the transmission engagement parts, thedownstream end of the cam surface should be connected to a radiallyinside end of the corresponding stop wall, while the upstream end of thecam surface should be connected to a radially outside end of thecorresponding stop wall.

When the prime mover 20 is in an operational state, if an externaltraction force is applied at the same time, for example the lawnmower 1is pushed manually, then the rotation speed of the wheels 12 increases,and the output members 32 coupled to the drive shafts 40 are driven viathe drive shafts to rotate at a faster speed. The stop wall structuredescribed above allows the output member 32 to rotate at a higherangular velocity than the input member 31 and transmission members 33.That is to say, the angular velocity of the stop walls is greater thanthe angular velocity of the transmission members 33 in abutmenttherewith, so the transmission members 33 move backwards relative to theabutted stop walls and thereby disengage, and slide along the camsurfaces 323. The cam surfaces 323 may press the transmission members 33back to the second position, such that the clutch 30 automaticallyswitches to the disengaged state. Thus, even if the transmission members33 are located in the path of rotational motion of the transmissionengagement parts 322 at this time, they will not cause interference torelative motion between the output member 32 and the transmissionmembers 33.

Such a configuration allows the output member 32 to move at a higherspeed relative to the input member 31 and the transmission members 33.For example, in the process of the lawnmower 1 being driven by the primemover 20, when it is necessary to turn, the operator can apply a pushingforce, so that the wheel 12 of the lawnmower 1 that is located at theouter side of the turning radius rotates at a faster speed, and a speeddifferential thus arises between the wheels 12 at the inner and outersides of the turning radius, to smoothly accomplish the turning action.Due to the presence of the clutch 30, even if the operator does not stopthe prime mover 20, it will not cause any interference or effect on thedriving of the wheel 12 located at the outer side of the turningradius—this is very convenient. When turning is complete, the operatorstops applying the pushing force, the rotation speed of the wheel 12falls until it is equal to or slightly less than the rotation speed ofthe input member 31 and transmission members 33 of the clutch 30, thetransmission members 33 are pushed to the first position by the inputmember 31, the clutch 30 automatically switches to the engaged state,and the lawnmower 1 can thus return to the pre-turning state of beingdriven by the prime mover 20. The clutch 30 is able to automaticallyswitch between states to adapt to changes in the rotation speed of thewheels 12, without any need to manually switch the state of the clutch30.

The above description of various embodiments of the present invention isprovided to a person skilled in the art for descriptive purposes. It isnot intended that the present invention be exclusively or limited to asingle disclosed embodiment. As mentioned above, those skilled in theart will understand various alternatives and variations of the presentinvention. Thus, although some alternative embodiments have beenspecifically described, those skilled in the art will understand, ordevelop with relative ease, other embodiments. The present invention isintended to include all alternatives, modifications and variants of thepresent invention described here, as well as other embodiments whichfall within the spirit and scope of the present invention describedabove.

1. Clutch, comprising: an input member, the input member beingconfigured to receive a driving force and rotatable about a rotationaxis under the action of the driving force, the input member having atleast one protrusion extending in a radial direction relative to therotation axis; an output member, the output member being configured tooutput rotational motion and having at least one transmission engagementpart; and at least one transmission member, the at least onetransmission member being configured to be movable between a firstposition in which it is engageable with the transmission engagement partand a second position of disengagement, the at least one transmissionmember being located in a path of rotational motion of the protrusion,and able to abut the protrusion and be driven to move to the firstposition, wherein displacement of the at least one transmission memberbetween the first position and the second position has a component inthe radial direction.
 2. Clutch according to claim 1, wherein the clutchfurther comprises a biasing member, which biases the at least onetransmission member towards the second position.
 3. Clutch according toclaim 2, wherein the biasing member is a spring, the spring having oneend coupled to the at least one transmission member, and another endcoupled to the input member or a mounting member for mounting the atleast one transmission member.
 4. Clutch according to claim 1, whereinthe at least one transmission member is able to abut the protrusion andbe driven to move to the second position.
 5. Clutch according to claim4, sharp bump is provided at an inner side of the at least onetransmission member, the sharp bump being able to abut the protrusionwhen the input member rotates in a direction opposite to a drivedirection.
 6. Clutch according to claim 2, wherein the clutch isconfigured such that the input member rotates through a predeterminedangle in a direction opposite to a drive direction when the outputtingof rotational motion is stopped.
 7. Clutch according to claim 1, whereinthe at least one transmission member moves in a plane perpendicular tothe rotation axis.
 8. Clutch according to claim 7, wherein the at leastone transmission member moves in the plane between the first positionand the second position along a straight line inclined relative to theradial direction.
 9. Clutch according to claim 1, wherein the protrusioncomprises three protrusions arranged at uniform intervals in thecircumferential direction about the rotation axis, and the at least onetransmission member comprises three transmission members arranged inone-to-one correspondence with the protrusions.
 10. Clutch according toclaim 1, wherein the transmission engagement part of the output membercomprises a stop wall extending parallel to the rotation axis, the atleast one transmission member abutting the stop wall to achieveengagement with the transmission engagement part.
 11. Clutch accordingto claim 10, wherein the stop wall extends substantially in the radialdirection.
 12. Clutch according to claim 10, wherein when the at leastone transmission member is located at the second position, the at leastone transmission member is located outside a path of rotational motionof the stop wall.
 13. Clutch according to claim 10, wherein the outputmember is provided with a cam surface extending parallel to the rotationaxis; the cam surface is located between two adjacent stop walls, andconnects a radially outside end of one of the stop walls to a radiallyinside end of the other adjacent stop wall, at least part of the camsurface being a curved surface.
 14. Clutch according to claim 1, whereinin the direction of the driving force, the angular velocity of rotationof the output member is greater than or equal to the angular velocity ofrotation of the input member.
 15. Clutch according to claim 1, whereinthe clutch further comprises a mounting member for mounting the at leastone transmission member, the mounting member being provided with anelongated slot defining a movement path of the at least one transmissionmember between the first position and the second position.
 16. Clutchaccording to claim 15, wherein the elongated slot comprises a curvedsurface, to allow the at least one transmission member to pivot in theelongated slot.
 17. Clutch according to claim 15, wherein the outputmember is provided with a recess, and at least one of the at least onetransmission member, the mounting member and the input member is atleast partially disposed in the recess; or the input member is providedwith a recess, and at least one of the at least one transmission member,the mounting member and the output member is at least partially disposedin the recess.
 18. Clutch according to claim 14, wherein the mountingmember is provided with a mounting slot formed as a sunken cavity, theinput member being accommodated in the sunken cavity.
 19. Clutchaccording to claim 14, wherein the mounting member is provided with adamping element, the damping element being configured to be able toprovide damping so that the mounting member tends to remain stationary.20. Clutch according to claim 19, wherein the damping element providesdamping by rubbing against a member other than the input member and thetransmission member.
 21. Clutch according to claim 19, wherein thedamping element is made of a rubber or silicone rubber material, andextends radially outwards relative to the mounting member.
 22. Workmachine, comprising a prime mover, at least one wheel and the clutchaccording to claim 1, the prime mover driving the input member of theclutch, and the output member of the clutch driving at least one of theat least one wheel to rotate.
 23. Work machine according to claim 22,wherein the work machine comprises two clutches arranged in amirror-image fashion, each clutch being coupled to at least onecorresponding wheel.
 24. Work machine according to claim 22 wherein, thework machine is a gardening tool.